A Low Power Active-Passive Noise Shaping SAR ADC

The traditional passive noise-shaping SAR ADC has low power consumption but weak shaping capability; while the active noise-shaping SAR ADC has strong shaping capability but high-power consumption. The typical active-passive SAR ADC still consumes considerable power due to the use of OTA amplifier in the active part. In this paper, an active-passive noise-shaping SAR ADC is designed by using floating inversion amplifier (FIA) to replace the traditional OTA amplifier in the active part, which achieves a strong noise shaping capability and low power consumption at the same time. The second-order active-passive noise-shaping SAR ADC circuit designed by a 180nm CMOS process achieves 14.6-bit ENOB with 400KS/s sampling rate and consumes only 28.9µW.